Direct Inguinal Hernia

Etiology

In contrast to the indirect hernia, a direct hernia is most often an acquired lesion.  It occurs when a weak spot develops in the lower abdominal musculature (the posterior floor of the inguinal canal) due to the normal and/or abnormal stresses inflicted by living and aging.  In adults, stresses such as lifting heavy of objects, frequent coughing or straining, pregnancy, and constipation can instigate hernia. 

Unlike indirect hernias, direct hernias traverse medial to the inferior epigastric vessels and are not associated with the processus vaginalis.  The hernia consists primarily of retroperitoneal fat.  Only rarely is a peritoneal sac containing bowel encountered.  Because there is typically no involvement of a sac, they do not protrude with the spermatic cord, and as such, have a lower incidence of incarceration or strangulation.

Risk Factors

Probably the largest single risk factor for developing an inguinal hernia is being male.  Men are almost 10 times more likely to develop an inguinal hernia than females.  Other factors (which mainly lead to an increased pressure in the lower abdomen) put the general population at risk.  They include:

Clinical Presentation

Like indirect inguinal hernia, direct inguinal hernias typically cause a bulge in the groin (at the top of or within the scrotum) and usually with increased abdominal pressure.  Like indirect hernias, they may or may not be painful (usually not).  By palpating the inguinal canal and asking the patient to cough while standing, one can usually elicit the hernia.  In fact, one can often times palpate an inguinal hernia without invaginating the scrotum (as is typically taught in medical school).  Rather, by placing one's fingers over the inguinal canal and asking the patient to cough, one can often feel the bulge against the lower abdominal wall.  As direct and indirect hernias are unreliably differentiated by physical exam alone, the need to invaginate the scrotum to feel into the inguinal canal is often more uncomfortable to the patient, than telling to the physician.  Rarely, palpation is not even necessary, as the hernia is large enough to be visualized.

Direct hernias (because of their acquired nature) tend to occur in older patients and those that are overweight.  Other factors that cause stress on the lower abdominal muscles can produce a hernia.